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      <h1>对象扩展方法-Object.is</h1>
      <p>1.用于判断两个值是否相等</p>
      <p>2.基本很少用,常用的是·===</p>
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    <script>
      console.log(NaN === NaN); //false
      console.log(+0 === -0); //true
      console.log(Object.is(NaN, NaN)); //true
      console.log(Object.is(+0, -0)); //false
    </script>
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